Sunrise 5:50 AM   Sunset 7:59 PM Moonrise 4:52 AM   Moonset 6:37 PM

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FXUS63 KILX 062347 AFDILX

Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 647 PM CDT Mon May 6 2024

KEY MESSAGES

- A line of thunderstorms will push through central Illinois late tonight into Tuesday morning...bringing gusty winds and downpours, as well as a few tornadoes possible.

- Scattered severe thunderstorms may re-develop Tuesday afternoon and evening.

- Confidence is growing concerning on a more significant and widespread severe weather event across much of central and southeast Illinois Wednesday afternoon/evening.

DISCUSSION
Issued at 258 PM CDT Mon May 6 2024

While a few showers persist in southeast/east-central IL this afternoon associated with a shortwave moving ENE up the Ohio Valley, this activity should gradually diminish this evening as a line of thunderstorms organizes in the central Plains late this afternoon and evening and sweep eastward toward central IL. Latest high-res models are fairly unanimous with this line arriving in far west- central IL around 2 AM a few hours past peak intensity. MUCAPE values are forecast to be as high as 2000 J/kg as this line moves into western MO/IA, down to 1000-1500 entering IL, and 750-1250 as it exits IL to the east around 9 AM. This instability is also increasingly likely to be elevated in nature as a stable layer develops near the surface. Nevertheless, there will be a chance for scattered severe wind gusts, especially west of the Illinois River where SPC has denoted a Slight Risk of severe thunderstorms, likely weakening to more isolated wind gusts as it weakens toward the I-57 corridor. A few tornadoes could also spin up along the line, again more likely toward western IL. There will likely be a lull in precipitation behind this line during the morning hours, but instability should return fairly quickly during the daytime hours, as mean surface-based CAPE forecasts increase to 1000-3000 J/Kg (highest southeast of I-70, lower northwest of IL River).
Outflow boundaries left behind from the early morning thunderstorm line could provide the convergence needed to start storms during the afternoon. Strong deep-layer shear of 50+ kt should support another round of severe thunderstorm development, containing large hail, locally damaging wind gusts, and a few potential tornadoes.
SPC continues a Slight Risk of severe storms from around Shelbyville to Champaign eastward, and a Marginal Risk for the remainder of central IL counties. Predominant high-res model guidance depicts these storms shifting southeastward out of the area by mid evening.

The closed upper low over the Northern Plains will linger into Wednesday, with another embedded shortwave likely inducing another convective system Wednesday. Current model continues to track this feature into central IL, perhaps a bit earlier with arrival in central IL Wednesday afternoon. 1500+ J/kg and 50+ kts deep layer shear continue to be forecast with this feature. SPC has depicted an Enhanced Risk for severe thunderstorm from near I-72 southward, and a Slight Risk for much of the remaining area to the north.

Following Wednesday's system, a wavy northwesterly flow aloft sets up for late week into the weekend, with the large scale trough axis shifting east of IL. Although occasional precipitation chances can be expected, amounts would be lighter, instability would be weaker for a decrease in thunderstorm activity.

Temperatures will remain warm through Wednesday, with highs around 80 Tuesday, and Wednesday, then a strong downtrend can be expected following Wednesday's cold front, with highs dipping back down to the 60s north of I-70 Thursday, and mid to upper 60s expected both Friday and Saturday. Lows into the 40s are forecast for much of the area each night Thursday night through Saturday night.
Temperatures will begin to trend back upward Sunday into early next week.

37

AVIATION
(For the 00z TAFs through 00z Tuesday Evening)
Issued at 646 PM CDT Mon May 6 2024

A line of thunderstorms currently stretching from Nebraska to Oklahoma will continue to move east overnight, crossing the central Illinois terminals late tonight. Storms should be in a decaying phase, but may still be strong producing gusty winds. A period of MVFR ceilings and briefly IFR ceilings will accompany the precip tonight. A warm front will lift north across the region Tuesday morning with SE winds ahead turning SSW behind. A few spotty showers and storms are possible during the day Tuesday, but low coverage precludes any mention in the forecast at this time.

Deubelbeiss

ILX WATCHES/WARNINGS/ADVISORIES
None.

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